Properly handle a NULL webwidget returned from WebViewClient::createPopupMenu

Source/web/PopupContainer.cpp

Index: Source/web/PopupContainer.cpp
diff --git a/Source/web/PopupContainer.cpp b/Source/web/PopupContainer.cpp
index 566d1fe73493f94d9ddf4968082c6f8226f5c308..f9c3e51c0dce554beb396faa77a33a83c1fa8987 100644
--- a/Source/web/PopupContainer.cpp
+++ b/Source/web/PopupContainer.cpp
@@ -472,6 +472,8 @@ void PopupContainer::popupOpened(const IntRect& bounds)
         return;
 
     WebWidget* webwidget = webView->client()->createPopupMenu(WebPopupTypeSelect);
+    if (!webwidget)
+        return;
     // We only notify when the WebView has to handle the popup, as when
     // the popup is handled externally, the fact that a popup is showing is
     // transparent to the WebView.